Fix some more ValueErrors

[packetcat]

Example error:

Traceback (most recent call last): File "/home/ss/dev/lazyreddit/lazyreddit.py", line 52, in r.hot(sr=subreddits, limit=10)]) File "/usr/local/lib/python2.6/dist-packages/narwal/reddit.py", line 230, in hot return self._subreddit_get(sr, None, limit=limit) File "/usr/local/lib/python2.6/dist-packages/narwal/reddit.py", line 211, in _subreddit_get return self._limit_get(_args, limit=limit) File "/usr/local/lib/python2.6/dist-packages/narwal/reddit.py", line 202, in _limit_get r = self.get(_args, *_kwargs) File "/usr/local/lib/python2.6/dist-packages/narwal/reddit.py", line 24, in wrapper return f(self, *args, *_kwargs) File "/usr/local/lib/python2.6/dist-packages/narwal/reddit.py", line 143, in get raise BadResponse(r) File "/usr/local/lib/python2.6/dist-packages/narwal/exceptions.py", line 29, in init super(BadResponse, self).init('{} received'.format(response.status_code)) ValueError: zero length field name in format